Hydrocarbon oil treatment



Dec. 24. 1940. -w. B. sHANLEY ETAL HYDROCARBON OIL TREATMENT- Filed July50. 1938 Patented Dec. 24, 1940 PATENT OFFICE HYDROCARBON OIL TREATMENTWilliam B. Shanley and Robert E. Sutherland, Chicago, Ill., assignors toUniversal Oil Products Company, Chicago, Ill., a corporation of DelawareApplication July 30, 1938, Serial No. 222,155

Claims.

This invention relates particularly to processes aimed at sweeteningsour distillates such as those produced in either the straight-run orcracking distillation of crude petroleums or their fractionsrespectively.

It is more specifically concerned with a particular method of operationin which granular sweetening reagents are employed in a highly effectivemanner from a practical and commercial standpoint.

The petroleum refining industry is familiar With numerous processes andreagents applicable to the conversion of the mercaptans present in lowboiling hydrocarbon fractions into relatively nonodorous di-alkyldi-suldes by reactions involving overall oxidation. The so-called doctortreating reagent is Well-known as Well as other processes involving theuse of cupric or other ic salts which are produced during the sweeteningstage then reactivated by controlled oxidation for further service. Someof the disadvantages of the plumbite method of treatment are concernedwith emulsion formation, the time required for the break when sulfur isadded to the primarily formed lead mercaptides to cause a separation oflead sulfide and the formation of the di-alkyl di-sulfides, and thetendency to use an excess of sulfur to hasten the break which increasesthe `sulfur content of the gasoline or naphtha undergoing treatment andform polysuldes which have a very deleterious effect on the anti-knockproperties of the gasoline.

Cupric and other salts of metals having higher and lower valences areemployed in various ways to eect the oxidation of mercaptans to di-alkyldi-suldes, sometimes in solution and sometimes as constituents ofgranular composites through which the sour distillates are percolated.The present process involves a specilic method of utilizing granularsweetening composites containing salts of metals at one of their highervalences which have been found commercially practical particularly inplants of relatively small capacity as measured by oil renery standards.

In one specific embodiment the present invention comprises a process forthe sweetening of sourv hydrocarbon distillates which comprises adding axed amount of a granular sweetening reagent to a body of sourdistillate, pumping the suspension in admixture with regulated amountsof air or other oxidizing gas through a filter to build up a cakethereon, recycling a portion of the filter effluent to further contactwith the sweetening reagent, separating residual gases, furthercontacting the distillate with stationary beds (C1. ISB- 29) of granularmaterials comprising reagents eiective in removing dissolved salts andcontinuing the process until the treating efficiency of the filter cakehas dropped below a practical level.

The more important features of the present process will now be describedinv connection with the attached diagrammatic drawing which showsingeneral side elevation Without regard to absolute or relativedimensions an arrangement of interconnected units in which the processmay be conducted. f

Referring to the drawing any distillate which is presumably thoroughlyvwashed with caustic soda or other alkalis to remove hydrogen sulfide isintroduced to the treating plant through a line I containing a valve 2and pumped by a pump 3 through a line 4 containing a valvev 5 through aheating element 6 disposed to receive heat from a furnace 1. Duringpassage through heating element 6 which lmay take the form of va heatexchanger if hot process fluids are conveniently available, thetemperature is preferably brought to about 85 F. which is the optimumwhen employing sweetening composites containing Cupric salts cfacharacter to be presently described. ln case of prevailingatmospherictemperatures oi the order of 85 F. or higher, the heating Will obviouslybe dispensed with. The present method of operation is'appilcable to thesweetening of sour distillates with any type of granular compositecontaining salts of metals at a higher state of valence, and temperatureof treatment will be varied according to the oxidizing and treatingeiciency of the particular compound or mixture of compounds chosen.

The incoming charge at the optimum temperature of treatment passesthrough line 8 containing valve 9 to slurry tank I0 to which a xedamount of granular sweetening composite is added in one portion or in anumber of small portions as the treatment may require. The tank may beprovided with any type of agitating or mixing device although these arenot shown in the drawing. The suspension of granular treating reagentinoil passes through line I I containing valve I2 to pump I3 whichdischarges through line I4 containing control valve I5 at a ratedependent upon the level in slurry tank IIJ as controlled by float I6and transmission line Il. The slurry passes through a mixer 29 which maycontain lilling or bailling material or any arrangement of perforatedplates to insure thorough mixing and contacting of the oil and thetreating reagent, after which the materials pass through line 30containing valve 3l to a lter press 32 which may be of any suitable typeof construction. According to the present process the sweetening reagentis permitted to build up a filter cake on the plates of a press and thesour oil is pumped through the lter cake at an optimum rate dependingupon the effectiveness of the reagent and the sourness of the distillateuntil sweetening is effected. Line 33 containing valve 34 permits thewithdrawal of any amount of liquid at this point and branch line 35containing Valve 36 permits the return ofl the filter efliuent to theslurry tank I9 in case sweetening is not effected by a single passagethrough the bed of reagent. Line 31 containing valve 38 is provided forthe returnl of a mixture of oil and air to an air separator 39 fromwhich the air is withdrawn through line 40 containing valve 4I and theliquid passes back to slurry tank l0 through line 42 containing valve43.

Prior to the passage of the slurry to mixer 29 a regulated amount of dryair at the approximate rate of 10 ou. ft./bbl. of sweetened distillateis added. This in effect causes a partial concurrent reactivation of thecupric or other ic salts and permits much longer periods of operationbefore reactivation is necessary. Thus air under pressure may beintroduced through line I6 containing valve I1' to ,water knock-out drumI8 which may contain filling or baiiiing material supported onperforated false bottom I9. In this treatment any mechanically entrainedwater will be `removed and Withdrawn through line 20 containing valve2|. The air at substantially 100% humidity at the temperature ofoperation then i passes through line 22 containing valve 23 to air drier24 which may have adsorbent or chemical drying materials such as fullersearth or calcium chloride respectively within the upper and lowerperforated plates 25 and 26. 'I'he function of this drier is to reducethe Water content of the incoming air to a low point since apparentlybest results are obtained when substantially no moisture is present. Thedry air passes through line 21 containing valve 28 to line I4 alreadydescribed.

When thecake of sweetening material which is permitted to build up onthe plates of iilter press 32 becomes too far spent for practicalpurposes, the stream of slurry may be diverted to other pressesconnected in parallel and the filter cake then removed from the pressinto a hopper 44 and reactivated in separate apparatus or disposed of ina manner suitable to its composition. By the use of filter presses inparallel the present process may be made substantially continuous.

The sweetened distillate, which inthe case of `copper salts frequentlycontains traces of color, due possibly to copper mercaptides, passesthrough line 45 containing valve 46 to an air Aseparator 41 from whichany entrained air may be vented through line 48 containing Valve 49.Line 50 containing valve 5|v permits the withdrawal of distillate orsedimentary materials at this point for test or other purposes.

The sweetened distillate then passes through line 52 containing valve 53tov pump 54 which discharges through line 55 containing control Valve 56which is actuated by float 51 through transmission 58 inaccordance withthe level in the air separator.

The distillate then passes through a bed of granular material insecondary treater 59 to improve color and remove dissolved salts. Thematerials'putilizable in the secondary treater comprise various metalsuliides, alone or on relatively inert supports, such as sodium sulfide,iron sulvcontaining cupric salts.

iide, zinc sulfide, etc. Zinc sulfide or composites containing the samehave been found especially effective for use in the secondary step ofthe treatment. Secondary treater 59 is provided with line BEI containingvalve 6| for the removal of liquid or sedimentary material and line 62con taining valve 63 for the withdrawal of sweetened and decolorizeddistillate.

While the present process may employ any type of granular sweeteningreagent comprising metal salts at their higher degree of valence it isparticularly suitable for the utilization of composites The followingtable shows the limit range of composition of composites which have beenfound particularly eiiective:

Limit compositions of sweetem'ng reagent l Per cent by weight* Ammoniumchloride (NI-i401) 25 5 Copper sulfate (CuSOaHzO) 25 5 Adsorbent, 6-30mesh 50 90 *Calculated on a dry basis except for the water ofcomposition of the crystalline copper sulfate.

Among the adsorbent materials which may be employed alternatively in thetreating composites, crushed silica, crushed rebrick, and fullers earthmay be mentioned, these materials being utilized in particle sizesbetween approximately 6 and 30 mesh. It has been found essential to theproper functioning of the treating reagent in the sweetening of sourgasolines to maintain the water content of the composite reagent Withinrather narrow limits. Experiments have shown that there is a deniteshortening of the life of the reagent if there is not sufiicient waterpresent to provide the necessary iive moles of crystallization for thecopper sulfate. The reactions which occur more or less simultaneously intreatment of the present character are given below:

(1) Sweetening reaction:

2CuCl2+RSH 2C`uCl+2HCl-l-RzSz (2) Reactivation reaction:

While the above equations do not represent the total of the reactionsoccurring, they may be taken asI typical. It will be seen from the firstequation that cupric chloride has been assumed to be the active reagentwhich is reduced to cuprous chloride and then simultaneously regeneratedby the combined action of hydrochloric acid and the oxygen of the air.One of the net results of these reactions is the generation ofconsiderable quantities of Water depending upon the amount of mercaptanspresent.

Composite treating reagents of the present character are preferably madeby the following general series of steps. The required amount of thecopper sulfate pentahydrate is reduced to a fine state of subdivision insome sort of grinding device such asv a ball mill until it isapproximately 200 mesh. An equal weight of ammonium chloride is added tothe same mill without removing the copper sulfate and the pulverizing iscontinued until the total material is of approximately 200-mesh iniineness; The ground and intimately commingled ammonium and coppercompounds are then removed and mixed in other apparatus with therequired amount of ad, sorbent which has been separately ground andsized to approximately 6-30 mesh. This final mixing is done in such amanner that there is substantially no further reduction in particlesizes and the solid ammonium and copper salts are adsorbed on the inertgranular material to form a surface coating thereon. The nal step in theprocess involves the addition of approximately 3% water by weight of thedry materials after which the mixing is continued until a'uniformcomposition is obtained. We have found that the addition of this amountof Water is sufficient to counterbalance the losses suffered by thecopper sulfate crystals during their grinding and to add a slight excesswhich is still on the safe side of the point corresponding to actualwetting.

One of the important features of the present process which constitutesan improvement in the older processes employing granular sweeteningreagents is that by the use of thin layers of reagent on the plates of afilter press, there is substantially no tendency to the channelingobserved When the same reagents are used in relatively tall cylindricaltreating towers. In the present instance sweetening will proceed untilthe water generated in the sweetening reagent has caused the solutionand removal of the active copper at which time the press is dumped andfresh granular treating reagent is added. Operations are also more rapidon account of the extended surface presented and the reduced pressuredrop.

The following characteristic example is illustrative of the resultsnormally obtainable in sweetening sour gasolines by the process of theinvention although not with the intention of limiting its scope in exactcorrespondence therewith.

A plant of the character described with reference to the drawing wasused on a sour cracked gasoline produced from Mid-Continent residualcharging stock. The plant was operated to treat 1200 bbl. gasoline perday using a copper sulfateammonium chloride-fullers earth composite asdescribed in the foregoing Specification, and the yield of gasoline perpound of sweetening reagent composite was 50 bbls. The gasoline from thecracking plant stabilizer was washed With 15 B. caustic soda to removehydrogen sulfide and heated to .a temperature of 85 F. before mixingWith the copper-containing sweetening reagent.

v Air was used in an amount of cu. ft./bbl. of net sweetened product,and a recycle ratio from the filter press back to the slurry tank ofapproximately 1:1 was maintained. The air was dried by passing throughclay and calcium chloride. A secondary treating reagent used to removedissolved copper compounds consisted of finely divided zinc sulfidemixed with fullers earth.

We claim as our invention:

1. A process for sweetening sour hydrocarbon distillate which comprisesmixing a solid granular sweetening agent With a portion of thedistillate, forcing the mixture through a filter press to build up acake of the sweetening agent on the filter press, vcontinuously passingadditional quantities of the sour distillate through the cake ofsweetening agent deposited on the filter press, repeatedly recirculatinga portion of the filter press effluent back through the filter press andeffecting the major portion of the sweetening of the distillate duringits passage through the filter press, and maintaining the continuouspassage of sour distillate through 4the filter press until the cake ofsweetening agent deposited thereon has substantially lost its sweeteningactivity.

2. 'I'he process as defined in claim 1 further characterized in that anoxygen-containing gas is commingled with said additional quantities ofsour distillate prior to the passage thereof through the filter press.

3. The process as defined in claim 1 further characterized in that saidsweetening agent comprises a cupric salt.

`Li. A process for sweetening sour hydrocarbon distillate whichcomprises mixing a solid granular sweetening agent comprising a cupricsalt with a portion of the distillate, forcing the mixture through afilter press to build up a cake of the sweetening agent on the filterpress, continuously passing additional quantities of the sour distillatethrough the cake of sweetening agent deposited on the filter press,repeatedly recirculating a portion of the filter press effluent backthrough the filter press and effecting the major portion of thesweetening of the distillate during its passage through the filterpress, continuously passing the remainder of the lter press efliuent toa treating zone and therein treating the same with a reagent capable ofremoving dissolved copper compounds therefrom, and maintaining thecontinuous passage of sour distillate through the filter press until thecake of sweetening agent deposited thereon has substantially lost itssweetening activity.

5. The process as defined in claim 4 further characterized in that airis commingled with said additional quantities of sour distillate priorto the passage thereof through the filter press and residual airseparated from said remainder of the filter vpress eflluent prior to theintroduction of the latter to said treating zone.

WILLIAMB. SHANLEY. ROBERT E. SUIT-IERLAND.

